This invention pertains to packages for integrated circuits.
Integrated circuit dies are generally housed in packages known as chip carriers to protect them from contact with foreign objects, and to provide leads for soldering them to printed circuit boards or other surfaces. Usually, the die is placed in a package with leads and connections are made from the die to the leads using small bonding wires. During assembly, several of these leads may be provided in one or more aggregate parts, called lead frames.
A lead frame is a piece of stamped or etched sheet metal that includes several leads that are connected together with removable ribs. These ribs hold the plurality of leads together during assembly of the package and thus simplify positioning of the leads. Once the package is assembled, the leads are separated by removing the ribs. Lead frames may be made by stamping or by etching, if the metal is thin enough with respect to the separation between leads.
It is known to allow epoxy to cure around a die and lead-frame at low pressures. It is also known to make this lower portion by molding lead frames with a central rib into a plastic body and then punching out the central rib along with a portion of the plastic body. An assembly method of this type is shown in U.S. Pat. No. 4,195,193 to Grabbe et al. entitled "Lead Frame and Chip Carrier Housing".